Generally, a DC motor includes a stator and a rotor mounted in the stator. The stator has multiple magnetic poles. The rotor includes a rotor core having multiple teeth, a commutator having multiple segments, and a rotor winding consists of multiple coils wound on the teeth of the rotor core and connected to the segments of the commutator. The stator further includes at least one pair of brushes for contacting the segments of the commutator, thus feeding power to the rotor winding. A pair of brushes includes a positive brush and a negative brush.
A traditional six-pole nine-slot eighteen-segment motor may have eighteen coils. Each coil is wound around a single tooth of the rotor core, with two terminals connected to two adjacent segments. Since the rotor core has nine teeth, each tooth has two coils wound around it. The rotor winding of the traditional motor forms six parallel branches connected between the positive brush and the negative brush, and each branch has three coils connected in series. Since each of the coils is formed by a large number of turns, the winding process of is time-consuming, thus resulting in high cost and slow motor manufacturing process.
Further, as the number of the turns of each coil is large, the coils should be wound by wires with small diameters, e.g., 0.6 millimeter (mm) or less, which are weak and are prone to be broken during operation of the motor.
Accordingly, it would be advantageous to reduce the winding process time of the motor and improve the reliability of the motor.